Voice over LTE

Discoveries upon discoveries, inventions upon inventions, all have led to very rapid changes in communication principles and technologies. Let’s not go too far back, I still remember vividly when possessing a remote-control-sized mobile phone that could only do voice and SMS services was such a luxury. But as demands grew and technological advancements were made, we have seen before our eyes the network evolution from 1G to 2G, 2.5G, 3G and now we are talking about 4G and even 5G!!! The most striking to me though is 4G which represented a paradigm shift in radio access technology architectures from circuit-switched or circuit and packet-switched networks to a completely packet-switched system (all-IP network).

My perfect example of a 4G network is Long Term Evolution (LTE). LTE’s possession of an all-IP-based network resulted in highly reduced CAPEX and OPEX, crazy data speeds, reduced latency, among many other benefits.


These LTE features has changed the intensity of internet activities such as live video streaming, real-time gaming, live TV, just to mention a few. But wait a minute, we still need to make calls right? Okay, so how will our calls be routed if LTE has kicked out into thin air the circuit-switched arm of the network that connects us to the PSTN? In the pursuit for higher data rates, did the developers forget that we still need to make phone calls and not just get lost with wicked speeds on the internet? Who knows!

Also, on the side of the mobile service providers, it has been reported that SMS and voice revenues represent about 70% of their business. We the customers can actually relax, no need to worry about how calls will be made on this all-new LTE network, because the service providers will definitely come up with a fast solution on how to keep the revenues coming in.

I guess it’s a true saying, “when there’s a will, there’s a way” or “no matter how difficult a situation is, there’s always a solution”, think I’m starting to sound religious.

Without thinking too far, we all are familiar with Skype, right? YES!!! Skype employs a technology known as Voice over IP (VoIP), which provides a means of having voice communication via the internet protocol rather than PSTN. Unlike traditional voice calls, which is analogous and uses circuit switching technology, VoIP uses packet-switching techniques. Packet switching involves converting the analogue voice signals into digital signals, packetizing them, transporting them through the network alongside data packets and then converting back to analogue signals (understandable to the human ears) at the receiver terminal.

This means that VoIP is geared towards voice and data integration; hence, they are able to share resources leading to reduced equipment, and they are able to achieve bandwidth optimization, since VoIP calls and data services can be done simultaneously.

Voila! This VoIP method of voice communication relies on the Internet Protocol which is at the bedrock of the LTE network.

Of course, there are other solutions on how the LTE network can support voice calls; here, I’ll just outline all possible methods:

  1. Circuit switched fall-back (CSFB): In order to make a voice call, CSFB employs certain processes and network elements which enables the network fall back to a 2G/3G circuit-switched connection.
  2. Simultaneous Voice and LTE (SV-LTE): This solution allows the operators to offer packet-switched LTE for data services simultaneously with circuit-switched voice services using a 2G/3G network.
  3. Over-the-top VoIP: OTT VoIP solutions include applications such as Skype. Quality voice communication through VoIP requires very high data rates such as provided by LTE to be comparable with the quality observed with PSTN. But under all load conditions, there is no guarantee on the quality of service, neither is there any room for handover to circuit-switched voice service in little/no LTE connectivity conditions.
  4. Voice over LTE via Generic Access (VoLGA): This solution is based on the existing 3GPP Generic Access Network (GAN) but using LTE as the access technology to 2G/3G networks. The aim of GAN is to extend mobile services over a generic IP access network.
  5. One voice initiative (referred to as VoLTE): This solution incorporates 3GPPs IMS Multimedia Telephony as the standard for delivering voice services on LTE network. This method has been accepted globally by mobile operators and organizations as the lasting method for delivering voice and messaging services on LTE. It brings in all the features of IMS culminating in a rich solutions delivery network. The merging of LTE/IMS implements true all-IP architecture.

Despite the ever-intensifying demand for data services, voice services still yields higher profit for the network service providers, as the relevance of voice communication cannot be over-estimated. NSPs have tried to provide VoIP services, geared towards protecting this voice revenue. But delivering VoIP services demands QoS levels better than the Best Effort (BE) structure that today’s IP networks offer. But with the advent of LTE, one can say there’s always a way forward.

A survey of voice solutions for LTE reveals that VoIP on LTE network in conjunction with IMS architecture is the best modus operandi. It merges the advantages of IMS and LTE functionalities. As NSPs leverage on these advantages, it will result in an upward boost of their business economies, while the consumers are set to experience rich multimedia solutions in “High Definition”.

Written by Adu Oluwadamilola

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